Flocculation-deflocculation steps in mineral wool-clay board formation



United States Patent 3,549,485 FLOCCULATION-DEFLOCCULATION STEPS IN MINERAL WOOL-CLAY BOARD FORMATION Lewis W. Eckert, Lancaster, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania N0 Drawing. Filed Mar. 4, 1968, Ser. No. 709,886 Int. Cl. D2111 3/00; D21h 3/68, /18 U.S. Cl. 162-152 4 Claims ABSTRACT OF THE DISCLOSURE In forming a board from a water slurry of clay and mineral wool, the slurry is fiocculated prior to being introduced onto the forming machine and is subsequently deflocculated on the forming machine by showering the surface of the sheet, just after it forms on the wire, with a solution of sodium carbonate, sodium bicarbonate or sodium hydroxide.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to boards formed from claymineral wool slurries and more particularly relates to boards formed by Fourdriniers from slurries of mineral wool and a clay having the clay characteristics of Mississippi M & D clay.

Descrption of the prior art Ollinger, U.S. application Ser. No. 466,477, filed June 23, 1965, now U.S. Pat. No. 3,371,134 relates to the manufacture of ceramic sound absorbing board products useful for ceiling tile and ceiling panels. Denlinger, U.S. application Ser. No. 149,035, filed in 1961, now U.S. Pat. No. 3,136,683 discloses that if sodium bicarbonate is added to the slurry of mineral wool and clay prior to board formation, boards of increased strength are realized.

SUMMARY OF THE INVENTION In accordance with this invention, it has now been discovered that if the slurry which is added to the headbox of a Fourdrinier is flocculated and if the board formed on the board forming machine is subsequently deflocculated by showering the surface of the water-laid sheet shortly after it has been formed and during free drainage, with a solution of a defiocculant, boards of improved strength are realized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 3,549,485 Patented Dec. 22, 1970 aid, namely a polyethylene oxide sold under the trade name designation Polyox by Union Carbide Corporation, which acts to further bind the mineral wool and clay. After the slurry has been formed and flocculated it is added to the head-box of a Fourdrinier machine from which point it flows onto the wire forming a water-laid sheet in which the water is present from the extent of from about 45% to by weight of the sheet. In forming the sheet, the water-laid web passes through a free drainage section, 'between compression rolls and then over a vacuum to give the final desired thickness and to reduce the water content to about 45 to 75 by weight of the sheet. The sheet is then passed through a dryer to remove the remainder of the water after which it is fired for a relatively short period of time, usually about ten minutes, at a temperature somewhere within the range of from about 1,000 F. to about 1,600 F. The product formed is a light-colored incombustable ceramic acoustical product having low density and good dimensional stability.

If, in addition to the above-mentioned ingredients, between about 0.50% and 9.0% by weight the total solids of sodium bicarbonate is added to the slurry prior to board formation, a board having improved strength is realized. This feature is disclosed in U.S. application Ser. No. 149,035 (Pat. No. 3,136,683) and, the disclosures of both U.S. application Ser. No. 466,477 and U.S. application Ser. No. 149,035 are incorporated herein by reference. However, this addition, prior to formation of the board has been found to interfere with the proper flocculation of the sheet and improper flocculation results in poor clay retention on board formation with attendant loss of board strength. In addition, the presence of sodium bicarbonate in the drainage water interferes with proper flocculation if the drainage water is re-used in slurry formation.

I have discovered that if a solution of sodium carbonate, sodium bicarbonate, or sodium hydroxide is showered onto the board after it has been formed on the wire but prior to the point at which most of the water has been removed, clay retention is maximized and boards having improved strengths are achieved. By adding the sodium bicarbonate, sodium carbonate, or sodium hydroxide solution by a water shower to the surface of the sheet as the stock flows out of the head-box onto the wire, the sodium carbonate, sodium bicarbonate, or sodium hydroxide becomes distributed throughout the sheet by the water which is being removed in the free drainage section and the vacuum phase which follow in board formation. The solution causes deflocculation of the formed sheet and the strength of the board thus formed and thereafter fired is measurably improved. When the defiocculating solution is added after the water-laid sheet has been formed, even though deflocculation occurs, the clay retention is not changed appreciably since, after formation, the smaller clay particles are retained by the closely-knit fibers in the waterlaid web.

In practicing the invention it is preferable to go through a two-stage flocculation. Thus the water slurry of mineral wool and clay is initially fiocculated by adding 0.1% to 0.8% by weight, based on the total solids, of a papermakers alum (a. hydrated aluminum sulfate) to the slurry 3 and mixing. At this point other desired additives such as minor amounts of starch may be added.

The fiocculated slurry is then further fiocculated just prior to board formation by adding and mixing a secondary fiocculant such as polyethylene oxide in the weight range of 0.01% to 0.2%, based on the weight of total solids in the slurry. This further flocculated slurry is then flowed onto the forming wire of the board forming machine to form the water-laid web of mineral fiber and clay.

As the primary flocculants, in place of papermakers alum, Fe (SO Ca(OH) or CaCl may be used.

Generally, any non-ionic or anionic polymeric flocculating agent may be used as the secondary fiocculant. Examples of such agents are Polyox (Union Carbide Corporation), a non-ionic polyethylene oxide, Accurac 24 (American Cyanamid), an anionic polyacrylamide and Polyial 295 (Stein Halland Company), an anionic polyacrylamide.

During the free-drainage stage of the board formation and while water saturates the water-laid web, the face of the water-laid web is showered with a water solution of a defiocculant. The del'locculant used is selected from sodium carbonate, sodium hydroxide and sodium bicarbonate. The concentration of the solution of defiocculant used is limited only by the solubility of the defiocculant and by the dilution necessary to give good distribution of the shower across the sheet. The rate of addition is adjusted to give more than 1% by Weight of flocculant. based on total solids in sheet. Optimum addition rates for NaOH and Na CO are about 2.5% by weight solids and for NaHCO about 5.0% by weight solids and usually no additional benefits are achieved at greater than 7%.

The following illustrates the invention.

14" x 14" x /8 handsheets were prepared using the TAPPI Standard T1001 sheet mold. The following ingredients were mixed for 10 minutes:

Percent by weight of Weight, grams total solids Water 25, 450 Mississippi M dz D clay 03 4D Tapioca Starch". 31 4 Paperinakers sin 3. 8 5 Mineral weoL 433 55. 5

After 9 /2 minutes mixing 123 grams of 0.25% Polyox solution was added to further fiocculate the mix. The fiocculated slurry was then added to the sheet mold and a sheet was formed by draining the water through the screen. When a defiocculating agent such as Na- CO was The following treatments were investigated:

The. amount of the deilocculant retained is diilieult to exactly determine. These values were obtained using final dry sheet weights and assuming the same percent retention oi other ingredients in all sheets. This is not true since the carbonate partially defloceulates the mix and could cause a slight loss oi other materials sueh as clay. The retention values shown are therefore minimum. Actual retention should be somewhat higher.

The following physical properties were measured:

TABLE II Dry properties Fired properties Den- Adjusted Den- Adjusted Sheet No. sity M0 R sity MO R MO R 417 460 1.95 212 223 406 -448 1. SK] 216 235i 357 382 1. 93 272 202 351. 373 1. 01 220 242 456 475 1. J7 230 237 A Fourdrinier run was made using the following formulation:

Percent by weight of total solids Mineral wool 57.5 40 Mississippi M & D clay 40.0

Tapioca starch 2.5

Lime 0.4

Polyox 0.05 4.5

Enough water was used to make the final consistency 4% solids.

The 29" wide machine was run a speed of 4.5 ft./min. Polyox was added to the stock after the fan pump, immediately before the machine. After about four feet of free drainage and while there was still free water on the surface of the forming sheet, a 2.6% Na CO solution was showered on the sheet across the width of the machine. The sheet was then tamped to help break up the Polyox floc, passed over vacuum boxes and pressed to a wet sheet thickness of 0.690" and 66% moisture content. The sheet was then dried and fired at 1,400 F. for six minutes. The first portion of the run was made without the Na CO shower and the last portion with the shower.

The following properties were obtained:

Two additional runs were made using the same formulation:

showering a solution of a defiocculant onto the surface of said draining sheet at a rate and concentration Another Fourdrinier run was made using alum, Al (SO -14H O as the primary flocculant instead of line (0.4% alum, direct replacement for 0.4% line).

sufficient to provide at least one percent by weight of defiocculant, based on the total solids in said sheet, distributed throughout said sheet, said defioc- TABLE V Dry properties Fired properties Adjusted Adjusted Density MOB. MOR Density MOR MOB.

NazCOs shower (2.6% NazCO:

addition):

Machine direction 1. 94 125 147 1. 93 200 214 Across direction 2. O3 170 181 1. 95 245 256 Units of Tables I-V:

Density=Lb./boa.rd it. Modulus of Rupture (M0 R)=Lb.lsq. in. (ASlM D1037fi4) Adjusted MOR, dry=MOR adjusted to 2.1lb./boardtt. Adjusted MO R, fired=MOR adjusted to 2.1 ib./board it.

formation portion of the operation. Because of the pres- 7 ence of deflocculant in such drainage water, the use thereof results in improper flocculation being achieved in the slurry used for sheet formation. This is evidenced, in production, by a falling off in board strength in boards made from production stock after the initial production and after drainage water containing deflocculant is reused in slurry formation. This disadvantage can be overcome by acid neutralization of the drainage water prior to reuse. It is desirable to use a mineral acid, hydrochloric, sulfuric or nitric, and to neutralize to an adjusted pH of between about 6.8 and 7.2.

I claim: 1. In a process for forming a mineral fiber-clay ceramic board product wherein mineral fiber and clay are slurried with water, formed into a water-laid sheet on the wire of a board forming machine and the sheet drained, dried and fired, the improvement comprising the steps of:

flocculating the clay and mineral fiber slurry by adding an mixing, based on the weight of solids in said slurry, from 0.1% to 0.8% by weight of a flocculant selected from the group consisting of a hydrated aluminum sulfate, Ca(OH) CaCl, and Fe (SO forming a water-laid sheet from said flocculated slurry and, while said sheet is being initially subjected to dewatering on said wire,

culant being selected from the group consisting of Na -CO NaHCO and NaOH.

2. The method as defined in claim 1 in which from 0.01% to 0.2% by weight, based on the weight of total solids, of a secondary flocculant selected from the group consisting of a non-ionic and an anionic polymeric floccuiating agent is added to and mixed with said slurry just prior to sheet formation.

3. The method as defined in claim 2 in which the primary flocculant is a hydrated aluminum sulfate, the secondary flocculant a polyethylene oxide and the defioccu' lant Na CO 4. The method as defined in claim 1 in which the drainage water is reused in forming additional slurry and in which the drainage water so reused is treated with a mineral acid to adjust the pH to 6.8 to 7.2.

References Cited UNITED STATES PATENTS 7/1962 Thomas 162115 3/1968 Denlinger 162152 FRANK W. MIGA, Primary Examiner F. FREI, Assistant Examiner 

